1). Field of the Invention
The invention relates to a substance mixture for a cofferdam material, to the material, and to the use and preparation thereof.
2). Background Art
A cofferdam is an aid customarily used in dentistry, for example for dental operations. Synonyms are rubberdam, stretch rubber, rubber cloth and rubber plate.
During dental treatment the cofferdam is arranged in the patient's mouth in the region of the tooth or group of teeth to be treated and can have an extremely wide variety of functions. For example, it may be used to protect the patient from unintentionally breathing or swallowing, it may provide protection from infection for the patient, attendants and dentist, and it may assist in providing an aseptic field of operation and in draining the area being treated, in holding back and protecting soft tissues and in improving visibility and in providing increased access; reference is made, for example, to Winkler, Kofferdam in Theorie und Praxis, Quintessenz-Verlags GmbH, 1991, for example, page 17, FIG. 7; and also Denis & Ott in Dtsch. Zahnarztl. Z., (1993) 303-308.
Such a cofferdam can additionally be provided with a holding device in order that it can be secured in the region of the tooth in the form of a square, rectangular or round protective element.
The main constituent of a cofferdam is usually natural rubber which is obtained from latex. For preparation, the liquid raw latex is coagulated to form a thin film which is subjected to heat vulcanization. The thin rubber material prepared in this manner is marketed in the form of sheets or rolls.
A great problem in the use of customary cofferdams obtained from natural rubber is allergic reaction. It is to be assumed that allergies are attributable to the complex composition of the latex and to additives that are used in the vulcanization of the latex.
DE-A-3 423 823 and EP-A-0 268 347 disclose the use as dental impression compounds of cross-linkable silicones having a content of silicic acid (as filler) and silicone processing auxiliaries. In accordance with DE-A-3 423 823, it is possible to provide a base paste and a catalyst paste that contains platinum as catalyst. The two pastes are mixed together for use and harden at room temperature (Examples 3 and 5). The teaching given by EP-A-0 268 347 corresponds to that prior art and uses platinum black as catalyst.
It is also already known from U.S. Pat. No. 5,098,299 to seal, repair and fit rubberdam with the aid of a composition that is a material having a content of, for example, polydimethylsiloxane, a filler, such as glass particles, a hydrophilising low molecular weight aliphatic glycol and a cellulose material for homogeneity. The plasticity of that material allows compounds introduced into the mouth to be fitted and shaped in situ (column 12 below to column 13 above), for which purpose light-curing materials are selected (column 10, line 33). The properties required of that known composition are said to be guaranteed, for example, for from 0.2 to 4 hours (Example 1).